1. Field of the Invention
The present invention relates to a method of determining the ability of a particular medium to absorb electromagnetic waves. The present invention also relates to an electromagnetic sensor for detecting foreign bodies in media circumscribed by limiting surfaces, such as concrete, breakwork, gypsum or wood, and which includes a transceiver unit to be positioned on a limiting surface of a medium, the transmitting antenna of which emits radar waves.
2. Description of the Prior Act
Radar apparatuses, in particular ground radars or GPR-systems (GPR-ground penetrating radar) are used in geodesic works for a long time. These apparatuses continuously emit electromagnetic waves necessary for effecting measurements as soon as the apparatus is actuated. If an emission power of, e.g., an impulse radar is insufficient for a particular examination of a material, the operator can, at his discretion, increase the emission power within predetermined limits. However, from the safety point of view, it is desirable to obtain, before the measurement proper, for a precise examination of a medium, in particular for tracking down the foreign bodies located inside the medium, an information of what type of an electromagnetic wave-absorbing material is located beneath a surface or a section of a surface subjected to examination by the electromagnetic sensor.
In addition to this prime object, there exists another safety-relevant aspect, namely, the emission power, which is emitted by a transmitting antenna, should not be released without a preliminary assessment of the absorption ability of the examined medium. Naturally, the most obvious solution was to integrate a touch switch into the transmitting antenna or in the antenna or transceiver unit. This touch switch could register the moment of placement of the antenna unit onto a limiting surface but could not recognize whether the material absorbs the emitted emission. In this way, upon the presence of, e.g., cavities, a radar pulse of a too big power would be emitted which, of course, is undesirable from the safety point of view.
Accordingly, the object of the present invention is to provide a method and an apparatus for, e.g., a GPR-system and, in particular for an electromagnetic sensor for examination of media circumscribed by limiting surfaces, such as concrete, gypsum, breakwork and the like, which would permit, at least roughly, to analyze the ability of the corresponding medium to absorb an electromagnetic emission before emitting a radar wave, the power of which is then can be correctly chosen, in an actual measurement process.